Lean-burn combustion dominates the current reciprocating engine R&amp;D efforts due to its inherent benefits of high BTE and low emissions. The ever-increasing push for high power densities necessitates high boost pressures. Therefore, the reliability and durability of ignition systems face greater challenges. In this study, four ignition systems, namely, stock Capacitive discharge ignition (CDI), Laser ignition, Flame jet ignition (FJI), and Nano-pulse delivery (NPD) ignition were tested using a single cylinder natural gas engine. Engine performance and emissions characteristics are presented highlighting the benefits and limitations of respective ignition systems. Optical tools enabled delving into the ignition delay period and assisted with some characterization of the spark and its impact on subsequent processes. It is evident that advanced ignition systems such as Lasers, Flame-jets and Nano-pulse delivery enable extension of the lean ignition limits of fuel/air mixtures compared to base CDI system.

Pistons for heavy duty diesel applications endure high thermal loads and therefore result in reduced durability. Pistons for such heavy duty applications are generally designed with an internal oil gallery — called the piston cooling gallery (PCG) — where the intent is to reduce the piston crown temperatures through forced convection cooling and thereby ensure the durability of the piston. One of the key factors influencing the efficiency of such a heat-transfer process is the volume fraction of oil inside the piston cooling gallery — defined as the filling ratio (FR) — during engine operation. As a part of this study, a motoring engine measurement system was developed to measure the piston filling ratio of an inline-6 production heavy duty engine. In this system, multiple high precision pressure sensors were applied to the piston cooling gallery and a linkage was designed and fabricated to transfer the piston cooling gallery oil pressure signal out of the motoring engine. This pressure information was then correlated with the oil filling ratio through a series of calibration runs with known oil quantity in the piston cooling gallery. This proposed method can be used to measure the piston cooling gallery oil filling ratio for heavy duty engine pistons. A preliminary transient Computational Fluid Dynamics (CFD) analysis was performed to identify the filling ratio and transient pressures at the corresponding transducer locations in the piston cooling gallery for one of the motoring test operating speeds (1200 RPM). A mesh dependency study was performed for the CFD analysis and the results were compared against those from the motoring test.

Composite pistons are often used in heavy duty diesel engines due to its good reliability and durability. Owing to the alternating loads, fretting wear usually happens on the mating surfaces between piston crown and skirt. In this paper, a fretting wear finite element model is developed to analyze the mating surface wear of composite piston of heavy duty diesel engine. The fretting wear model predicts the wear depth evolution for each working cycle based on Archard model and mesh updating technique, which is validated by previous pin and disk contact experiments. The wear evolution of the top contact surface of piston skirt is simulated according to engine operating condition, and fretting wear life is estimated by the decreasing process of crown-skirt connecting bolt preload. Effects of the shape of piston skirt top surface is also evaluated. In the end, the rationality of fretting wear model is validated by durability tests of diesel engine.

To meet the demand for greater fuel efficiency in passenger vehicles, various strategies are employed to increase the power density of light-duty SI engines, with attendant thermal or system efficiency increases. One approach is to incorporate higher-performance alloys for critical engine components. These alloys can have advantageous thermal or mechanical properties at higher temperatures, allowing for components constructed from these materials to meet more severe pressure and temperature demands, while maintaining durability. Advanced alloys could reduce the need for charge enrichment to protect certain gas-path components at high speed and load conditions, permit more selective cooling to reduce heat-transfer losses, and allow engine downsizing, while maintaining performance, by achieving higher cylinder temperatures and pressures. As a first step in investigating downsizing strategies made possible through high-performance alloys, a GT-Power model of a 4-cylinder 1.6L turbocharged direct-injection SI engine was developed. The model was tuned and validated against experimental dynamometer data collected from a corresponding engine. The model was then used to investigate various operating strategies for increasing power density. Results from these investigations will provide valuable insight into how new materials might be utilized to meet the needs of future light-duty engines and will serve as the basis for a more comprehensive investigation using more-detailed thermo-mechanical modeling.

A design process was defined and implemented for the rapid development of purpose-built, heavy-fueled engines using modern CAE tools. The first exercise of the process was the clean sheet design of the 1.25 L, three-cylinder, turbocharged AMD45 diesel engine. The goal of the AMD45 development program was to create an engine with the power density of an automotive engine and the durability of an industrial/military diesel engine. The AMD45 engine was designed to withstand 8000 hours of operation at 4500 RPM and 45 kW output, while weighing less than 100 kg. Using a small design team, the total development time to a working prototype was less than 15 months. Following the design phase, the AMD45 was fabricated and assembled for first prototype testing. The minimum-material-added design approach resulted in a lightweight engine with a dry weight 89 kg for the basic engine with fuel system. At 4500 RPM and an intake manifold pressure of 2.2 bar abs., the AMD45 produced 62 kW with a peak brake fuel-conversion efficiency greater than 34%. Predictions of brake power and efficiency from the design phase matched to within 5% of experimental values. When the engine is detuned to 56 kW maximum power, the use of multi-pulse injection and boost pressure control allowed the AMD45 to achieve steady state emissions (as measured over the ISO 8178 C1 test cycle) of CO and NO x +NMHC that met the EPA Tier 4 Non-road standard without exhaust after-treatment, with the exception of idle testing. PM emissions were also measured, and a sulfur-tolerant diesel particulate filter has been designed for PM after-treatment.

Two-stroke engines are capable of providing very high power density levels in a cost effective, easy-to-maintain package. They are, however, typically susceptible to higher levels of hydrocarbon emissions, lower durability, and a shorter lifecycle when compared to four-stroke engines. These detriments are easily overlooked in some military applications where power density is paramount, but most commercial two-stroke engines require specialized consumable lubricant. Typical military applications strive to minimize their logistics “trails,” which includes minimizing the variety of fluids they require. As a result, there has been very limited success in fielding small two-stroke engines for military use. As a preliminary study, MIL-PRF-2104K Single Common Powertrain Lubricant (SCPL, a four-stroke heavy diesel engine oil) was utilized as the consumable lubricant (in place of conventional two-stroke oil) in a liquid-cooled, semi-direct fuel injected, spark-ignition, two-stroke engine. Empirical data was collected to study the impact of the oil on deposit build-up, power, wear, combustion stability, and fuel conversion efficiency. Over 147 hours of operation were logged and analyzed. The performance of the engine on SCPL was consistent with conventional two-stroke oil and showed no degradation over the test duration. Brake specific fuel consumption was not negatively impacted with SCPL. Increased deposit build-up in the exhaust ports and on the spark plugs were the primary negative impacts of the SCPL oil. Spark plugs with hotter classifications and modification of the oiling rate resulted in a reduction of soot accumulation and spark plug fouling.

Blending cellulosic biofuels with traditional petroleum-derived fuels results in transportation fuels with reduced carbon footprints. Many cellulosic fuels rely on processing methods that produce mixtures of oxygenates which must be upgraded before blending with traditional fuels. Complete oxygenate removal is energy-intensive and it is likely that such biofuel blends will necessarily contain some oxygen content to be economically viable. Previous work by our group indicated that diesel fuel blends with low levels (&lt;4%-vol) of oxygenates resulted in minimal negative effects on short-term engine performance and emissions. However, little is known about the long-term effects of these compounds on engine durability issues such as the impact on fuel injection, in-cylinder carbon buildup, and engine oil degradation. In this study, four of the oxygenated components previously tested were blended at 4%-vol in diesel fuel and tested with a durability protocol devised for this work consisting of 200 hrs of testing in a stationary, single-cylinder, Yanmar diesel engine operating at constant load. Oil samples, injector spray patterns, and carbon buildup from the injector and cylinder surfaces were analyzed. It was found that, at the levels tested, these fuels had minimal impact on the overall engine operation, which is consistent with our previous findings.

Durability is a prime concern in the design of hydraulic systems and fuel injectors [1–3] thus an accurate prediction of impact velocities between components and the flow through them is essential to assessing concepts. Simulation of these systems is difficult because the geometries are complex, some volumes go to zero as the components move, and the flow at a single operating condition generally spans Reynolds numbers less than 1 to more than 10 4 [4–8]. As a result of these challenges, experimental testing of prototypes is the dominant method for comparing concepts. This approach can be effective but is far more costly, time consuming, and less flexible than the ability to run simulations of concepts early in the design cycle. A validated model of a fuel injector built from publicly available data [1] is used to present a new approach to modelling hydraulic systems which overcomes many of these obstacles. This is accomplished by integrating several commercially available tools to solve the physics specific to each area within the fuel injector. First, the fuel injector is simulated using a 3D CFD simulation integrated with a 1D CFD system model. The flow in various regions of the injector is then analyzed to determine if the fluid models in these areas can be simplified based on the flow regime. Based on this analysis, a combination of models is assembled to improve the quality of the simulation while decreasing the time required to run the model. The fuel injector is simulated using a multibody dynamics model coupled to a reluctance network model of the solenoid and several fluid models. The first is a 3D CFD simulation which uses novel mesh refinement techniques during runtime to ensure high mesh quality throughout the motion of components, to resolve the velocity profile of laminar flows, and to satisfy the requirements of the RNG k-ε turbulence model and wall functions. This approach frees the analyst from defining the mesh before runtime and instead allows the mesh to adapt based on the flow conditions in the simulation. Due to the highly efficient meshing algorithm employed, it is possible to re-mesh at each timestep thus ensuring a high quality structured mesh throughout the simulation duration. Then a 3D FEM solution to the Reynolds Equation and a statistical contact model is employed to solve for the squeeze films between components and to allow separation and contact between bodies in the control valve. These detailed simulations are integrated with a 1D flow model of the fuel injection system. The results from the detailed coupled simulations are compared to the results from simpler 1D models and measured data to illustrate under which operating conditions a more advanced technique incorporating 3D CFD is worth the additional computational expense versus a traditional 1D model.

Anaerobic digesters are capable of producing methane-rich biogas from animal manure and also offer the advantages of controlling odors, reducing pathogens, and minimizing the environmental impact of the waste. Unfortunately, biogas is contaminated with hydrogen sulfide (H 2 S), a highly corrosive gas that is not compatible with many stock engine component materials. As a result, conventional engines can fail after several months of exposure to raw biogas. No small or medium piston engine-generators (&lt;100 kW e ) are currently available that can use this fuel without pretreatment to remove the H 2 S — a process that adds complexity, cost, consumables, and maintenance. As a result, many smaller digester installations simply flare the biogas rather than extracting any useful work from the fuel. Mainstream Engineering is developing a biogas-tolerant engine-generator (BTEG) that can use raw biogas without pretreatment to remove H 2 S. The development program involved a combination of approaches — materials replacement, coatings, engine control strategy changes, lubrication system changes, and additional sensors. A prototype 25 kW BTEG has been developed using a Ford DSG 2.3 L natural gas engine as the demonstration platform. In this paper, we report on performance testing of the baseline unmodified engine-generator and the BTEG. Measurements of fuel consumption, exhaust temperature, in-cylinder pressure, and exhaust gaseous emissions were made using several synthetic biogas mixtures (60–80% CH 4 /balance CO 2 ) and pure methane. Because the methane fraction in biogas can change with digester conditions and weather — a method of estimating the biogas composition on the fly and adjusting the spark timing to compensate for the variability has been demonstrated. We also report on limited (100 hr) durability testing of the modified engine using fuel containing 3,000 ppmv of H 2 S. During this test, the oil was analyzed to track acidification of the engine oil and monitor the accumulation of sulfur or any wear metals.

Alternative fuels research has been on going for well over many years at a number of institutions. Driven by oil price and consumption, engine emissions and climate change, along with the lack of sustainable fossil fuels, transportation sector has generated an interest in alternative, renewable sources of fuel for internal combustion engines. The focus has ranged from feed stock optimization to engine-out emissions, performance and durability. Biofuels for transportation sector, including alcohols (ethanol, methanol…etc.), biodiesel, and other liquid and gaseous fuels such as methane and hydrogen, have the potential to displace a considerable amount of petroleum-based fuels around the world. First generation biofuels are produced from sugars, starches, or vegetable oils. On the contrary, the second generation biofuels are produced from cellulosic materials, agricultural wastes, switch grasses and algae rather than sugar and starch. By not using food crops, second generation biofuel production is much more sustainable and has a lower impact on food production. Also known as advanced biofuels, the second-generation biofuels are still in the development stage. Combining higher energy yields, lower requirements for fertilizer and land, and the absence of competition with food, second generation biofuels, when available at prices equivalent to petroleum derived products, offer a truly sustainable alternative for transportation fuels. There are main four issues related to alternative fuels: production, transportation, storage, handling and usage. This paper presents a review of recent literature related to the alternative fuels usage and the impact of these fuels on fuel injection systems, and fuel atomization and sprays for both spark-ignition and compression-ignition engines. Effect of these renewable fuels on both internal flow and external flow characteristics of the fuel injector will be presented.

Improvement of internal combustion engine emissions and performance by the introduction of a reducing gas such as hydrogen has been the subject of research in recent years. The approach reduces engine exhaust emissions and improves fuel consumption. The gas may be introduced into the engine intake or upstream of the exhaust catalyst for different effects. To date, the technique has not been implemented due to the need for onboard storage or generation of hydrogen that complies with suitability for automotive applications. In industrial processes and stationary applications, reforming reactors are well known, highly efficient, and durable means to convert liquid fuels such as diesel into hydrogen or other reducing gas mixtures (synthesis gas). Efficiency and durability for thousands of hours is required for these applications for economic viability. For an automotive application, however, in addition to the above features, fast transient response (e.g. during start up and turndown), compactness, and low cost are also required — while maintaining sufficient durability for the application. Also, the need for liquid water common to reactions such as steam reforming or auto-thermal reforming are impractical for automotive applications. A waterless catalytic partial oxidation approach avoids this shortcoming but is not without its own set of problems. Material durability, fuel/air mixing, coke avoidance and reliable ignition means are among the challenges for a practical automotive hydrogen production solution. The catalyst for reacting the fuel must be tolerant to sulfur content common to fuels in use today, and must have resistance to fouling by carbon formation. To overcome these challenges, Precision Combustion, Inc. (PCI) has developed a diesel-fueled waterless catalytic partial oxidation reformer with efficiency and size suitable for onboard synthesis gas production at low cost. The goal of the development effort was to produce a novel mechanical design with the high efficiency of stationary reformers in a small package which could be operated with low parasitic loss from balance of plant components to maintain high engine efficiency. The reactor design (size, form factor) is discussed, along with performance data showing transient and steady state response of the prototype reactor. Catalytic partial oxidation (CPOX) of heavy fuels such as diesel poses unique challenges, relating to coking and fuel conversion efficiency, which have been addressed and presented in this paper.

Turbocharger performance optimization on passenger car engines is particularly challenging, especially in case of severe engine downsizing and downspeeding. On high performance engines (e.g., heavy duty truck applications) turbocharger speed measurement is usually performed with the aim of maximizing engine power and torque, limiting turbocharger over-speed, which is harmful for its durability and reliability. This solution is too expensive for passenger cars, and the turbocharger speed sensor is typically not available. In this work, an innovative and low cost sensing chain for the rotational speed evaluation of the turbocharger is applied. With this information, obtained via an acoustic sensor, a new turbocharger control architecture has been developed to optimize turbocharger performance, in order to improve engine output torque under full load conditions. After a brief description of the new sensing chain and of the electronic components developed to manage this kind of information, the paper shows the new control architecture that takes advantage of the turbocharger speed information. Moreover, experimental results on a small turbocharged Diesel engine for passenger car applications are presented, demonstrating the achieved benefits.

Piston ring wear is a major factor determining a diesel engine’s life. A ring is subjected to wear between its front face and the cylinder wall as well as at the interfaces between the ring and groove top and bottom flanks. In many modern engines, ring and groove wear are becoming more of a limiting factor for ring durability than face wear. The focus of this paper is on ring to groove side wear only. In this paper two fundamental mechanisms for ring/groove side wear are identified: (1) wear due to piston secondary motion and (2) wear due to ring twist. The time in the cycle where each of these mechanisms results in maximum wear is shown. Then the effect of ring static twist and the resulting effect on the pressure distribution around the ring are studied. The pressure distribution affects the force acting on the ring that causes the ring/groove side wear. It is also shown that the pressure distribution and the resultant wear can be influenced by the land diameter below the piston ring. Progressive wear is also studied, showing a good correlation between predicted wear and measured wear on both ring sides and groove sides. It is noted that as the corner of the ring/groove wears, the ultimate wear of the ring side can accelerate by a phenomenon named pressure infiltration. Pressure infiltration occurs because the bottom side of the ring groove wears exposing more of bottom side of the ring to lower pressure force. This ultimately causes a higher difference between the high pressure above the ring and the low pressure below the ring. As a result, the net force acting on the ring increases and wear increases. In addition to the study of the first ring, the second ring wear was studied. A comparison was made between the top ring and second ring groove side wear (RGSW) predictions. Also the effect of the second ring static twist on both top and second ring/groove side wear is described in detail.

Increasing durability, preventing knocking combustion, improving fuel efficiency and reducing pollutant emission characterize the needs for modern internal combustion engine design. These factors are highly influenced by the power cylinder system design. In particular, the piston ring to cylinder bore contact force distribution around the circumference of the piston rings must be optimized under all running conditions. To accomplish this, the ring manufacturers make the ring curvature non-constant along the circumference. Most existing analytical tools are not able to simulate the variation along the ring circumference. In order to improve the understanding of this contact distribution and provide a high-fidelity ring design tool, a three-dimensional finite element piston ring model was developed to accomplish this variation. The modeling procedure and results are presented in this work. Experiments using a commercially available ring with negative ovality were conducted to validate the model. The ring free shape profile and the ring cross-section geometries were used as inputs to the model. Typical piston ring groove and cylinder wall temperatures were also model inputs to characterize thermal influences on the ring/bore interface forces. The ring/bore conformability was analyzed as a function of the ring radial displacements, cylinder bore constraint forces and thermal load changes to the ring. The model output showed radially separation gaps between the ring front face and the bore. This analysis provides an insight to evaluate the piston ring design. Together with an optimizer, the model can be used as a ring design tool to predict the ring free shape with a specified constraint force distribution pattern. Examples are given to demonstrate the capabilities of this numerical analytical tool. In addition, the 3D ring model can be used to improve the accuracy of existing lubrication, friction and wear analysis tools and therefore improve the entire internal combustion engine power cylinder system design.

Environmental regulation and high fuel cost are among the leading driving forces behind the demand of energy efficient vehicles. Together with new engine hardware technologies, engine oil is expected to significantly contribute to improving vehicle fuel economy. New fuel-efficient engine oils are often formulated with advanced additives and low viscosity base oils. Understanding the lubrication performance at key engine components such as the cam and follower in valve train systems becomes critically important to ensure engine durability with the new fuel-efficient low viscosity oils. A full numerical mixed lubrication analysis of the cam and roller follower pair is conducted using the three dimensional line contact mixed elastohydrodynamic lubrication (EHL) model. The results show significant effects of surface roughness, topography, slide-to-roll ratio, and viscosity grade on lubricant film, contact pressure, and subsurface stress.

Ongoing efforts to reduce CO2 and other pollutant tail pipe emissions have led to escalated demand for diesel-electric hybrid bus powertrains in Europe, similar to the trend in passenger car markets. This is fuelled by public expectations and initiatives by various European governments to reward bus fleet operators for reduced in-city emissions and noise thus improving air quality and wellbeing of the general population. This paper describes the engineering efforts that developed a Euro VI certified diesel engine system, catering for series hybrids operating under ‘charge-depleting’ as well as ‘load following’ battery management strategies. The development team delivered improved fuel economy whilst dealing with requirements around legislation, unique customer duty cycles and engine mechanical robustness. Focus was placed on capturing requirements from a diverse range of sources and harmonising them to develop a technical solution fit for purpose in day to day operation that differs from validation cycles and standard drivetrain operation. In order to deliver a field-ready solution, application specific tuning and validation processes had to be defined and developed. This was achieved through close coordination with the European bus OEMs and their chosen hybrid system suppliers. Six-sigma tools were used to highlight key expectations and drive technical solutions. At a system level the focus was on OBD reliability, exhaust after-treatment management, controls functionality, hardware durability and tail pipe emissions. Performance targets including the number of start-stops per hour, idle management and engine speed-torque ramp rates were defined. Drive cycle simulations helped define optimal engine and hybrid system operating strategies followed by physical testing to further optimise these running points. Vehicle-level validation was completed through field testing, specific European bus test cycles, as well as under exceptional scenarios encountered in real world use. This exercise was designed to find and solve interface and OBD issues. Integration challenges in the areas of engine speed-torque control, diesel particulate filter management and HVAC control were addressed. The outcome is the release of a bespoke Euro VI diesel engine package, which enabled the hybrid bus system to exceed customer expectations. This integrated system operates on a set of optimised parameters delivering efficient sub system behaviour including aftertreatment management, engine protection and operating state control. It handles the full range of real-world vehicle operation with improved fuel economy, frequent start/stop operation and enhanced driveability.

The heavy duty diesel (HDD) engine market continues to strive for improvements in engine efficiency and durability which places ever increasing development demands on the power cylinder unit. One of the methods being developed to help meet these demands is coated cylinder bore technology. By applying a coating to the inner diameter surface of a cylinder liner the wear on the liner can be significantly reduced. The reduction in liner wear is not however the only advantage that this technology can offer. Liner coatings can also offer corrosion protection, reductions in wear on the running surface of the rings, improved scuff resistance, and enable improvements in the efficiency of the engine. New piston ring technologies will be valuable in maximizing these advantages and their contribution will be detailed. The system must be properly designed to take full advantage of all of these opportunities. In this paper both the advantages and difficulties coated liners present will be explored by evaluating the impact on the liner, rings and the fuel consumption. This paper will additionally provide details regarding the different liner coating technologies being developed today. To support these recommendations the system’s performance characteristics will be demonstrated through rig testing and engine performance measurements.

Under normal operating conditions, engine crankshaft bearings experience variations in oil film temperature due to shearing of the oil film. This can have a negative impact on the bearing operating life since the viscosity of the lubricant is temperature dependent. In the current study, a thermo-elastohydrodynamic lubrication (TEHL) analysis has been conducted using an in-house specialized simulation package called SABRE-TEHL. This advanced simulation tool has been used to optimize a new bearing design feature leading to a significant temperature reduction, which in turns increases the robustness of the system.

Off highway Tier 2-4 emissions requirements for high speed, high horsepower diesel engines (&gt;750 h.p.) have driven substantial engine, after-treatment and fuel system design improvements. Modern high pressure common rail (HPCR) fuel systems are being applied by engine manufacturers through use of increased injection pressure, precision injection timing, and multiple injection events to achieve emissions targets. In the field, careful attention to diesel fuel quality is now required by the end user to avoid problems with performance, reliability and durability of the fuel systems and after-treatment. Ultra-fine filtration and complete water separation are essential to maintain the fuel clean and dry. Internal Diesel Injector Deposit (IDID) formation due to degradation of the fuel and unintended consequences of additives must also be avoided. This is a voice of a fuel consumer and fuel system integrator to fuel suppliers and end customers on challenges encountered and countermeasures developed to achieve better fuel filtration, water separation, fuel cleanliness practices and end user education.

Improving engine cooling performance requires sophisticated and intelligent engine cooling design especially when interactions of all engine parts are to be considered. The cooling system would highly influence engine thermal efficiency, durability and engine design criteria. Several attempts have been made by engine designers to improve the cooling design during the past decades, each with particular purpose considerations. In this paper, based on the cylinder head flame face of an existing heavy duty medium speed diesel engine, three other flame face cooling systems are designed, modeled and changes are implemented using a three dimensional computer aided design modeling software. Modeled cylinder head flame face cooling concepts are experiencing the effect of cooling passages geometry changes on performance of thermal efficiency, effective subcooled regions and other resultant factors. A detailed coupled computational fluid dynamic and thermal finite element analysis for one cylinder bank assembly is performed several times; paying special attention to the risky areas to get comparative results to assess the flame face cooling designs. Engine specifications and loading conditions together with the engine performance data are available from test rig. Initial and boundary conditions have been determined through a global model simulation and analysis. The subcooled nucleate boiling heat transfer computation is carried out using the boiling departure lift-off model. In order to obtain the temperature for components under consideration, a comprehensive thermal analysis has been performed coupling with the detailed CFD analysis to reach an accepted value through transferring data between the CFD and FEA software. This method leads to an accurate prediction of the wall temperature and heat flux. It is observed that proper cooling design could improve wall temperature and thermal stress related phenomena significantly. The advantages and disadvantages of each concept are discussed and preferred flame face design is demonstrated. Calculated results of original design are validated with test cell records.